Chapter 8 - Discrete Random Variables

Which of the following is NOT a discrete random variable?

One that is uncountably infinite

The standard deviation of X is the ___________ __________ of the _____________ of X.

Square root, variance

If X and Y are independent, then True/False: Variance of (X-Y) = Variance of (Y-X)

True

True/False: Mx-y = Mx - My

True

The mean cost of a box of Cheerios Oat Crunch is $4.00 and the variance is 0.35. If the price increase by 25 cents a box, what is the new variance?

0.35

Suppose X is a discrete random variable with mean 10 and variance 4, and Y is a discrete random variable with mean 20 and variance 9. We do not know whether X and Y are independent. True/False: we can find the variance of X+Y with only the information we are given

False

Let X = time waiting in line at a restaurant to get a seat in minutes. What are the units of the variance of X?

No meaningful units

Suppose X = number of 1 foot long steps taken in one hour by a person working in a bank. Suppose the mean of X is 300 and the variance is 64. If you change the units from feet to inches, you multiply by 12. What is the new standard deviation?

Square root of (12^2 x 64)

Everyone at Bob's diner makes $12.00 per hour. Let X = salary of an employee at Bob's diner. What is the mean of X?

$12 per hour

The mean cost of a box of Cheerios Oat Crunch is $4.00. If the price increases by 10% what is the new mean?

$4.40

If the variance of X is 10, what is the variance of 4x + 20?

160

Which of the following terms represents "all possible values of a random variable and how often you expect them to occur?"

Probability distribution

Everyone at Bob's diner makes $12.00 per hour. Let X = salary of an employee at Bob's diner. With this information, can you find the variance of X?

Yes